SAN FRANCISCO (CBS SF / CNN) — A covert state-backed social media campaign run from China has sought to undermine ongoing demonstrations in Hong Kong, according to information released by Twitter and Facebook on Monday.

Some accounts called demonstrators “cockroaches” or compared them to Islamic State terrorists. All the offending accounts have been taken down from Twitter and Facebook.

Twitter said it identified a network of more than 900 accounts that “were deliberately and specifically attempting to sow political discord in Hong Kong, including undermining the legitimacy and political positions of the protest movement on the ground.”

This is the first time tech companies have pointed the finger at Beijing for covert efforts to influence messaging around the Hong Kong protests. Democracy demonstrators have massed throughout Hong Kong for 11 consecutive weekends.

Protesters take part in a rally as they march on a street on August 18, 2019 in Hong Kong. (Anthony Kwan/Getty Images)

Twitter initially identified the network and shared details about the accounts with Facebook. Facebook then identified about a dozen pages, accounts and groups on its platform that were tied to the operation.